Electrical power systems are often built from arrays of smaller components such as battery cells, photocells, photovoltaic panels, and fuel cells. For example, fuel cells are often combined into units called “stacks” in which the fuel cells are electrically connected in series and separated by electrically conductive interconnects, such as gas separator plates which function as interconnects.
Fuel cells are typically combined to form a stack in a linear array (configured horizontally or vertically) in which the component fuel cells are electrically connected in series to obtain a preset voltage. A fuel cell stack may contain conductive end plates on its ends. A generalization of a fuel cell stack is the so-called fuel cell segment or column, which may contain one or more fuel cell stacks connected in series (e.g., where the end plate of one stack is connected electrically to an end plate of the next stack). A fuel cell segment or column may contain electrical leads which output the direct current from the segment or column to a power conditioning system. A fuel cell system can include one or more fuel cell columns, each of which may contain one or more fuel cell stacks, such as solid oxide fuel cell stacks.
In the operation of a voltage array, it is often desirable to know the voltage of each component of the array. For example, it may be desirable to know the output voltage of each fuel cell within a fuel cell stack to determine the health of a stack, to provide data for optimization tools, and to determine when maintenance is required. It is also important to minimize impact that the measurement device has on the parameters that it is measuring.